# How to tell whether to fix hairline crack in automobile radiator or to replace it? **URL:** \ **Category:** Factual Questions\ **Created:** [June 5, 2007, 2:28pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840 "2007-06-05T14:28:06Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 5, 2007, 2:28pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/1 "2007-06-05T14:28:06Z")
Yup … it’s the self-same vehicle as in [this thread](http://boards.straightdope.com/sdmb/showthread.php?t=422003). I noticed a bit of steam coming from under my hood after my thankfully-short commute Friday. Upon opening the hood, steam and tiny bubbles were coming out of a 3-inch crack at the very top of the radiator, on the side away from the engine and upper hose flange. Thankfully, the crack is way up high … so coolant is not leaking out when the truck is parked. At the moment, I add water to top off the radiator for every trip to and from work (about a 10-15-minute drive each way on 35-mph surface streets – no open road). I realize that is diluting the coolant/water mixture, but it’s only been a stopgap measure until I can determine what level of repair I am dealing with. I understand that sometimes cracks in radiators can be successfully sealed. My GQ is this: _how can I tell the difference between a crack that’s a good candidate for sealing, and one that necessitates a new radiator?_ That a new radiator would cure all is a given … the issue, as it so often is, is the cost of the repair. I am hoping that the location of the crack works to my advantage, as there is no slow-leaking when parked. TIA for any advice or anecdotes. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [June 5, 2007, 3:08pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/2 "2007-06-05T15:08:39Z")
I would check with experts at your local radiator repair shop. Not familiar with your vehicle, but if the crack is in the top cap, and it sounds as though it might be, and the material is brass, it could probably be soldered with success. If it’s aluminum I believe it would have to be welded. Replacing the top cap is another option that would probably require removal of the whole unit. And that’s where labor costs could eat you up. Regardless of the cracks location, I’d never depend on any sealant to last a respectable amount of time. Limp home from the lake, sure give it a try. Other than that a permenant repair is required. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 5, 2007, 3:09pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/3 "2007-06-05T15:09:54Z")
Is it a crack in the tank or in the core (the tubes with the fins)? If it is in the tank, is the tank plastic or metal? ---
**Author:** ![Like\_Fry](https://avatars.discourse-cdn.com/v4/letter/l/3da27b/32.png) [@Like\_Fry](https://boards.straightdope.com/u/Like_Fry)\ **Post date:** [June 5, 2007, 3:20pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/4 "2007-06-05T15:20:00Z")
To reiterate previous posts, replace the radiator, dont trust a reseal or patch. It will just end up costing more money in the long run. Fry ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 5, 2007, 3:33pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/5 "2007-06-05T15:33:40Z")
[QUOTE=Rick] Is it a crack in the tank or in the core (the tubes with the fins)? If it is in the tank, is the tank plastic or metal? [/QUOTE] It’s the top of the tank, but off to one side quite a bit (the left side when leaning over the hood and facing the engine), well away from the radiator cap. The entire crack is visible and easily accessible without removing components. AFAICT, the tank is plastic. **GaryM** … is there any other kind of “permanent repair” other than radiator replacement? There are two things I’m hoping are in my favor in my effort to delay radiator replacement (if that is inevitable): 1. I can get by _only_ driving the 3 miles to work and back every day, topping off the radiator twice daily (only not with water going forward, but with a coolant/water mix). I am concerned that this could (or will ☹ ) make the crack larger – the question then is “how fast?”. 2. the location of the crack, being way up high and away from the cap. If I can get a few more months (3 or 4) out of the radiator by employing temporary fixes, then I can afford the $400-600 I’ll need for a new radiator plus labor. But right now, I’d have to lay the truck up in lieu of shelling out that much at one shot. ---
**Author:** ![Like\_Fry](https://avatars.discourse-cdn.com/v4/letter/l/3da27b/32.png) [@Like\_Fry](https://boards.straightdope.com/u/Like_Fry)\ **Post date:** [June 5, 2007, 3:49pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/6 "2007-06-05T15:49:45Z")
I fear you only risk making the problem worse the more you drive it, which can lead to much more expensive repairs. If your handy with tools replacing the radiator yourself is easy. Also, a decent radiator shop should be able to find you a new replacement for ~200 depending on application. Check online for the manual (pdf most likely) or a walkthrough from someone that has done it before. Also, I am sure you can find recomendations from a group that has a board for your vehicle type, which will include good parts to use at good prices, and the aformentioned walkthrough. Fry ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 5, 2007, 4:04pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/7 "2007-06-05T16:04:07Z")
Interesting replies to a similar query at [this link](http://ask.metafilter.com/15934/Car-Repair-filter-Leaking-radiator-help). The requestor over there added pictures of his radiator crack – I should add that the crack in my radiator is nowhere near that big: The raw-egg trick? Doesn’t sound like a great idea: > [@](#): > > I’m no car buff, but on Mythbusters, they used a raw egg in the radiator to stop the leak. > > Not sure what the long term effects or benefits are, but supposedly it works. Several enthusiastic nods for JB Weld – here’s the most comprehensive one: > [@](#): > > Do this on a cold radiator: > > 1. Wire brush the area well. > 2. Clean the area with Iso. Alcohol or Vodka. > 3. Mix and apply JB Weld to the crack. > 4. Toss in some Stop-Leak for good measure. > 5. Enjoy your trip. > 6. Start saving up for a new radiator. > > I’ve used JB Weld to repair a cracked block effectively, (the patch lasted 20,000 miles until I sold the car) so I don’t think the heat is going to be an issue. Lastly, a response of interest because I don’t think I’m driving far enough to overheat my car so long as the radiator is topped off before short trips. Only light wisps of steam escape from the crack when I drive to and from work … I’ve been opening the hood and having a look upon parking yesterday and this morning. AFAICT, the only reason for the copious steam Friday was because the coolant level was low: > [@](#): > > If you are not over heating, you could try running **a non-pressurized cooling system**. If you have a lever radiator cap, leave the lever up. Otherwise you would have to find a way to make the cap not seal. Most radiator caps have a rubber ring for a seal. You can just cut the rubber seal (but this ruins the cap if you ever do get the radiator fixed) or find a way to make it not seat properly. Pressurization of the cooling system just gives you a higher boiling point for your coolant. **If you are not pulling a heavy load up a mountain at high elevation, you would probably be OK**. :dubious: ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 5, 2007, 4:23pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/8 "2007-06-05T16:23:04Z")
A leak in a plastic tank pretty much means a replacement radiator is called for. JB Weld may provide you with a semi-permanent fix, assuming you do everything right. A raw egg or alumaseal will only work if there is no pressure in the system, meaning you are leaving the cap loose. Call around to some local radiator shops, I think your guesstimate of $400-$600 is a bit high. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 5, 2007, 4:39pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/9 "2007-06-05T16:39:42Z")
[QUOTE=Rick] A leak in a plastic tank pretty much means a replacement radiator is called for. [/QUOTE] Thanks for the advice. 🙂 [QUOTE=Rick] JB Weld may provide you with a semi-permanent fix, assuming you do everything right. [/QUOTE] Sounds like it’s very easy to screw up the application of JB Weld … but the instructions above seem straightforward :shrug: [QUOTE=Rick] A raw egg or alumaseal will only work if there is no pressure in the system, meaning you are leaving the cap loose. [/QUOTE] Wow … I hadn’t taken the raw-egg thing seriously. Surely, that won’t last a few thousand miles, even if I can likely get away with a non-pressurized cooling system? [QUOTE=Rick] Call around to some local radiator shops, I think your guesstimate of $400-$600 is a bit high. [/QUOTE] I will – hope I’m wrong about the price of a replacement. Thanks for taking the time to respond. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 5, 2007, 5:03pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/10 "2007-06-05T17:03:14Z")
A suggestion had been made to use [Lab-Metal](http://www.bearingsbeltsandchain.com/fpdetails_0906_labmetal.asp) instead of JB Weld. No mixing, easy application, withstands temperatures of 350 degrees, fine for non-metal surfaces. I’m not seeing the downside of this stuff, except that it is aluminum-based – could there be a corrosion concern? My understanding is that coolant wears down aluminum over time. ---
**Author:** ![Harriet\_the\_Spry](https://avatars.discourse-cdn.com/v4/letter/h/e56c9b/32.png) [@Harriet\_the\_Spry](https://boards.straightdope.com/u/Harriet_the_Spry)\ **Post date:** [June 5, 2007, 5:07pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/11 "2007-06-05T17:07:46Z")
Recent radiator repairs of the \*\*Spry-mobile \*\* came to $365, for a Honda Accord. $245 parts, $120 labor. This was at a garage we have used for a while as not the cheapest but very competent with a good reputation for integrity. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 5, 2007, 5:30pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/12 "2007-06-05T17:30:22Z")
Are products like [Bar’s Leaks Radiator Stop Leak](http://www.barsproducts.com/C16_R6.htm) not recommended? ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 5, 2007, 5:31pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/13 "2007-06-05T17:31:54Z")
[QUOTE=bordelond] Thanks for the advice. 🙂 Sounds like it’s very easy to screw up the application of JB Weld … but the instructions above seem straightforward :shrug: [/quote] Actually it is quite easy, but you need to have a super clean and DRY surface to apply it to, and it needs adequate cure time. I don’t recall the cure time, check the package for more details. About the only other way to screw up JB Weld is to get the proportions wrong. It needs to mix 50/50 not 75/25. 😃 > [@](#): > > Wow … I hadn’t taken the raw-egg thing seriously. Surely, that won’t last a few thousand miles, even if I can likely get away with a non-pressurized cooling system? More like it will get you home from a trip and that is about it. So what happened with the starter? ETA: I have never had good luck with Bar’s leak. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 5, 2007, 5:40pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/14 "2007-06-05T17:40:56Z")
[QUOTE=Rick] So what happened with the starter? [/QUOTE] Well … for now, I’ve changed my driving habits to accomodate the symptom. I just don’t start the engine when it’s hot anymore. Starts up fine every time. [QUOTE=Rick] ETA: I have never had good luck with Bar’s leak. [/QUOTE] As long as there’s no real risk of damaging other components, I’m willing to give Bar’s Leaks a shot as a medium-term solution. If I try that and it fails, I’m only out a few bucks. I’m much more interested in the Lab-Metal stuff … checking on distribution and such now. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 6, 2007, 2:04pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/15 "2007-06-06T14:04:40Z")
[QUOTE=bordelond] As long as there’s no real risk of damaging other components, I’m willing to give Bar’s Leaks a shot as a medium-term solution. If I try that and it fails, I’m only out a few bucks. [/QUOTE] Bar’s Leak’s instructions strongly suggest a radiator flush before use. My current plan will be to drive the truck to and from work for 10 more days. That takes me to payday, and allows me to absorb the cost of the flush. In the interim, I will check the crack twice daily (as I’ve been doing) to make sure it’s not getting longer. If I see it getting worse, I’ll loosen the radiator cap to depressurize the cooling system, which I can apparently do safely for short trips. Thanks for the advice, all! ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [June 6, 2007, 4:35pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/16 "2007-06-06T16:35:33Z")
[QUOTE=bordelond] That takes me to payday, and allows me to absorb the cost of the flush. [/QUOTE] I wouldn’t be spending much money on a temporary repair. Replacing a radiator can be a fairly simple job to do yourself, and a radiator from a place like AutoZone should be fairly inexpensive (and good enough for an old truck). Take a look at the radiator and see how hard it will be to remove. It may be surprisingly easy. I have had plastic tanks replaced before, but with inexpensive radiators available from auto parts stores, I wouldn’t do it again. Check online to see what a radiator would cost. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [June 6, 2007, 5:01pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/17 "2007-06-06T17:01:56Z")
[QUOTE=Dag Otto] I wouldn’t be spending much money on a temporary repair. Replacing a radiator can be a fairly simple job to do yourself, and a radiator from a place like AutoZone should be fairly inexpensive (and good enough for an old truck). Take a look at the radiator and see how hard it will be to remove. It may be surprisingly easy. I have had plastic tanks replaced before, but with inexpensive radiators available from auto parts stores, I wouldn’t do it again. Check online to see what a radiator would cost. [/QUOTE] At AutoZone, there are three replacement radiators available for my make/model/year truck, rangins from $125-160. The flush is about $90 or less, as I haven’t called around yet. The Bar’s Leak was $3.50. I need to have a closer look at the radiator and the stuff around it … I’m looking at it enough as it is already checking out that crack all the time. I should go to the library or Barnes & Noble and flip through a Chilton’s. Nissans usually have a bunch of stuff in the way of various under-the-hood components, which can discourage even decent home mechanics (which I am not). There’s also the I-might-miss-reconnecting-comething factor ☹ … although it seems like only one hose in, one hose out. ---
**Author:** ![A.R.Cane](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@A.R.Cane](https://boards.straightdope.com/u/A.R.Cane)\ **Post date:** [June 6, 2007, 5:09pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/18 "2007-06-06T17:09:05Z")
[QUOTE=Dag Otto] I wouldn’t be spending much money on a temporary repair. Replacing a radiator can be a fairly simple job to do yourself, and a radiator from a place like AutoZone should be fairly inexpensive (and good enough for an old truck). Take a look at the radiator and see how hard it will be to remove. It may be surprisingly easy. I have had plastic tanks replaced before, but with inexpensive radiators available from auto parts stores, I wouldn’t do it again. Check online to see what a radiator would cost. [/QUOTE] I agree. Generally, it’s easier to change out a radiator in a pickup than a car. If you have some mechanical ability, you should be able to do the job. If you have one problem w/ your current radiator, it’s likely you’ll have more. I’d bet that you’re just putting off the inevitable, and wasting money, in trying to patch up the old radiator. ---
**Author:** ![scabpicker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scabpicker/32/8268_2.png) [@scabpicker](https://boards.straightdope.com/u/scabpicker)\ **Post date:** [June 6, 2007, 7:12pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/19 "2007-06-06T19:12:03Z")
Here is another cautious vote for replacing the radiator yourself. It is usually the easiest engine work that you will do. The one caveat I can think of is, if it is an auto transmission, make sure that the transmission cooler is not integral to the radiator, that makes it a little more complex. This is not really likely, as I have only seen this on older American cars. If it is a manual, I say go for it without worries. Flipping through the Chilton repair manual to get the gist of the process usually can’t hurt, but be aware that they are sometimes wrong. I had a fun time looking for my EGR valve while troubleshooting a problem on my Ranger, only to eventually find that my particular engine never had one. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 6, 2007, 7:17pm UTC](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840/20 "2007-06-06T19:17:03Z")
[QUOTE=scabpicker] Here is another cautious vote for replacing the radiator yourself. It is usually the easiest engine work that you will do. The one caveat I can think of is, if it is an auto transmission, make sure that the transmission cooler is not integral to the radiator, that makes it a little more complex. This is not really likely, as I have only seen this on older American cars. [/QUOTE] 😕 Off the top of my head I cannot think of any auto trans car that does not have the oil cooler in the radiator. [Next page](https://boards.straightdope.com/t/how-to-tell-whether-to-fix-hairline-crack-in-automobile-radiator-or-to-replace-it/406840.md?page=2)